Injection-molded circuit carriers, the so-called molded interconnect devices (MID) are currently used in many ways in the electronics industry. Such circuit carriers are designed to be three dimensional (3D-MIDs).
The goal of the 3D-MID technology is to combine electrical and mechanical functions in a single component. The circuit paths in this case are integrated into the housing and in this way replace conventional circuit boards. The weight and package size can be effectively reduced and the integration of sensors and the like is simplified.
There are various technologies for producing 3D-MIDs. Among these are two-component injection molding, hot stamping, in-mold decoration and additive or subtractive laser structuring.
U.S. Patent Application Publication No. 2004/0241422, German Patent DE 10132092, and European Patent Application EP 1 274 288 disclose methods for laser structuring of circuit paths. In this method circuit path structures are generated on an electrically nonconductive carrier material, where these paths consisting of metal seeds and a metallization subsequently applied to these seeds, where the metal seeds resulted from the raising of electrically nonconductive metal compounds that are contained in a very finely divided form in the carrier material, by electromagnetic radiation. In doing so the electrically nonconductive metal compounds are formed of thermally very stable inorganic metal compounds that are insoluble and stable in aqueous acidic or alkaline metallization baths and that remain unaltered in regions not irradiated by the laser. The inorganic metal compounds that are used are temperature resistant so that they remain stable after exposure to soldering temperatures. The circuit paths are reliable and easy to manufacture and have a very high bond strength.
However, a problem of this method is that in the laser structuring operation portions of the substrate surface and thus also the metal seeds are removed and/or destroyed because of temperature development, and can become deposited on other sites on the substrate surface. In the subsequent metallization of the circuit paths that were produced not only do the circuit path structures become metallized, but the unintentionally deposited metal seeds do as well. These unplanned deposits can lead to a degradation of the selectivity of the circuit path structures and thus to problems in the electronic components due to short circuiting.
In order to avoid these problems the distances between the structured circuit paths can be chosen to be so great that deposited metal seeds will not have any troublesome effects in the subsequent metallization. This solution to the problem, however, leads to deficient circuit densities and thus leads to great disadvantages.